function fib(n){
    if(n < 2){
      return 1
    }
    return fib(n-1) + fib(n-2)
  }
let t_start = (new Date()).getTime()
fib(40)
let t_end = (new Date()).getTime()
msg.echo("js用时" + (t_end-t_start) + "ms")